The Multipass Amplification Of Low Frequency Static Phase Error Correction Study

With the scale of high power solid-state laser facility becoming larger and larger, there are more and more optics used in a beamline. Because the polishing quality of the - optics is not ideal and the material used to make the optics is non-uniform, wavefront aberration caused by the optics draws more and more attention. This paper mainly concludes research on correction of static low-frequency wavefront aberration induced by Nd:glass in the Multipass Amplifier. The followings are the main achievement in this paper:1. The main sources of wavefront aberration in high power solid-state laser facilities are analyzed and important specifications to describe wavefront aberration are introduced. After comparing some important techniques for correcting wavefront aberration, the importance of doing research on static wavefront aberration correcting method is clarified.2. The model is established to get the scale length of a wavefront, which is a characteristic parameter for a wavefront. The wavefronts of existing Nd:glass amplifiers are analyzed with this model. As a result, the model of low-frequency aberration induced by Nd:glass amplifiers is got. On the base of low-frequency aberration model some results are achieved such as the tendency of focal spot size changing as the RMS phase gradient changes and the characteristics for the scale length.3. The simulation model of the beamline is set up and the propagating process is analyzed in the beamline. The correlation coefficient of two wavefronts is newly used to describe and estimate the adding result of them. Based on the propagation simulation, some laws of low-frequency wavefront adding are found. As a result, two kinds of new methods to correct static low-frequency aberration are put forward. The first kind is using a countervailing mirror and the other is self-correction method.4. The method of using a countervailing mirror to correct static wavefront aberration is introduced. By adducing a new concept梕quivalent phase plate, this correcting method is simulated and an wavefront aberration correcting experiment is done.5. The theoretical foundation of the self-correcting method is further discussed and an experiment to testify this method has been done. At last,a program model is introduced to execute this self-correcting method in large laser facility to choose and put the Nd:glass amplifiers.